Make ~/, round, ceil, floor, truncate return ints. Remove toInt.

samples/swarm/swarm_ui_lib/touch/Scrollbar.dart

Index: samples/swarm/swarm_ui_lib/touch/Scrollbar.dart
diff --git a/samples/swarm/swarm_ui_lib/touch/Scrollbar.dart b/samples/swarm/swarm_ui_lib/touch/Scrollbar.dart
index 4516c99f971aee8ce14c9e72028716eb3de16c38..6a0d69abacec5f62b13fb64bc3f49be13c64f8cf 100644
--- a/samples/swarm/swarm_ui_lib/touch/Scrollbar.dart
+++ b/samples/swarm/swarm_ui_lib/touch/Scrollbar.dart
@@ -209,9 +209,9 @@ class Scrollbar implements ScrollListener {
       _currentScrollStartOffset -= delta;
       if (_currentScrollVertical) {
         x = _scroller.getHorizontalOffset();
-        y = _currentScrollStartOffset.toInt();
+        y = _currentScrollStartOffset.truncate();
       } else {
-        x = _currentScrollStartOffset.toInt();
+        x = _currentScrollStartOffset.truncate();
         y = _scroller.getVerticalOffset();
       }
       _scroller.setPosition(x, y);